This is a large ashlar block that appears to be reused in part of a pier base construction along with SU 6195. This ashlar pier base is one of several that line the area directly north of road SU 7019. The piers extend along the entire southern limit of room G-1, suggesting they may have once supported columns that formed a portico structure north of the road SU 7019.
Photo from east
Photo from west
photo from south
Room G-20